Effects of spatial nonuniformity of superconducting-tunnel-junction ion detectors on mass Spectroscopy

Spatial uniformity of superconducting tunnel junction detectors with a size of 200 mu m is improved by increasing Al thickness of the Nb/Al proximized electrodes in an energy range of 5-10 keV. which is in the same order as an acceleration energy in time-of-flight mass spectroscopy (TOF-MS). It has been confirmed in the TOF experiments with Ta ions and Th clusters that the proximized junction detectors clearly separate different ionic states and multi-hit events in impact energy spectra, and moreover can reveal the difference in ion species or ion-surface collision dynamics. However, a better spatial uniformity is not always good for TOF-MS, possibly because a detector with the thicker Al layers has a lower superconducting energy gap, which results in an improper detector operation because of a temperature rise.due to heat radiation, or the states of the detector surfaces are different.